The invention is directed to a process for the production of 4-chloro-butanals of the formula ##STR2## in which R is hydrogen or a straight or branched chain alkyl group having 1 to 4 carbon atoms, e.g., methyl, ethyl, propyl, isopropyl, n-butyl, sec.butyl or t-butyl. The 4-chloro-butanals of formula (1) can be condensed with salicylhydroxamic acid, which optionally can be substituted, to form 2,3,4,4a-tetrahydro-1OH-1,2-oxazino-[3,2-b]-[1,3]-benzoxazin-10-ones (cf. Arzneim.-Forsch. Drug Res. 27(I), No. 4 (1977), page 760). (S)-4-chloro-2-methyl-butanal furthermore is an important intermediate product for the production of synthetic vitamin E. (see German OS No. 2720775).
It is already known to produce 4-chlorobutanal by hydrogenation of 4-chloro-butyric acid chloride in the presence of a poisoned noble metal catalyst (J. Am. Chem. Sec. Vol. 73 page 1365 (1951)) or in the presence of an alloy catalyst (German OS No. 2506157), yield of 4-chloro-butanal, however, by these known processes is relatively poor.